Don't get too excited. The Friday start is based on the fact that for them, Friday is like Sundays are for Christians. Friday is a holy or sabbath day for them. They'll be less prepared for an attack if they are all kneeling on their prayer mats.
As for a date...your guess is as good as the next, but I would say take a look at a Friday near the darkest point of the lunar calendar. We like darkness, and we like surprise (or at least an enemy that is preoccupied with what direction East is come sundown). Kind of makes it easier to sneak in and drop a shitload of bombs on them.
